1. Field of the Invention
The present invention relates to a method, apparatus, and storage medium for controlling a disk drive. More particularly, the invention relates to a method, apparatus, and storage medium for controlling a track seek servo in a disk drive.
This application claims the benefit of Korean Patent Application No. 10-2006-0012600, filed on Feb. 9, 2006, the subject matter of which is hereby incorporated by reference.
2. Description of the Related Art
A hard disk drive (HDD) includes a plurality of magnetic transducers, often referred to as “read/write heads”, adapted to read data from and/or write data to one or more rotating disks. (Hereafter, only a single “disk” will be described, bearing in mind that multiple disks or disk surfaces might be used). Read operations are generally accomplished by sensing a magnetic field associated with the surface of the disk. Write operations are generally accomplished by selectively magnetizing the surface of the disk. Data is written (i.e., recorded) in a plurality of sectors respectively included in concentric tracks designated on the surface of the disk. Each disk track is identified by a unique number. Tracks having the same number form a cylinder around the disk. Thus, each track may be further defined using a cylinder number.
Each read/write head is typically mounted on a slider combined with a head gimbal assembly (HGA). Each HGA is attached to an actuator arm. The actuator arm is operatively combined with a voice coil adjacently located to a magnetic assembly. The voice coil and the magnetic assembly forming a voice coil motor (VCM). The HDD typically includes a driving circuit supplying drive current to run the VCM, and a related controller. As driven by the applied current, the VCM rotates the actuator arm to move the read/write head over the surface of the disk.
During read/write operations, the HDD may perform a seek routine moving a read/write head from one cylinder to another. During the seek routine, the VCM controls movement of the read/write head to position it over a new cylinder location above the surface of the disk. During this operation, the controller performs a servo control routine ensuring that the read/write head moves to a correct cylinder location and track center.
It is clearly preferable to minimize the amount of time needed to read data from or write data to the disk. Thus, during a seek routine, each read/write head must be moved to a new cylinder location within the shortest reasonable time period. This design objective requires that stabilization of the HGA be performed in a minimum of time.
In general, to quickly move a read/write head to a target track, a seek servo control routine is performed using a rectangular acceleration trajectory. However, the square wave control signal used in this approach often includes a harmonic high frequency wave component which may cause mechanical resonance in the HGA. Such mechanical vibration may cause the mechanical components and/or assemblies to vibrate at a corresponding high natural frequency. This outcome produces acoustic noise, generates an undesirable vibration, and extends the time requires to achieve HGA stabilization. The mechanical resonance potentially generated by the conventional square wave control signal, thus, increases the total time (including stabilization time) required to read data from and/or write data to the disk.
In light of this problem, a seek control technique using a sinusoidal acceleration trajectory has been developed. However, although the seek control technique using a sinusoidal acceleration trajectory significantly reduces noise and vibration, the seek control technique also requires a complex algorithm to calculate the acceleration trajectory. Execution of this complex algorithm requires a great deal of time and adversely extends the time required to execute read/write operations.